WED has nothing to do with MED ^^"

You need to copy the texture files out of the separated folder, directly into the folder where your 3ds or fbx file is!
Best would be:
Open the 3ds file in a modeling tool like 3dsmax, c4d or whatelse.. and export it again as 2011-FBX File. The FBX now includes the texture mapping..

Open MED -> File -> Import from FBX (2011) -> Save as MDL

This MDL File can be loaded into WED and you´re happy